1. Field of the Invention
This invention relates to gas turbines, and more particularly, to a process and an apparatus for the control of liquid fuel for gas turbines using piston pumps which transport the fuel to the fuel injector.
2. Background Information
On gas turbines, there are systems in which the fuel is injected into the combustion chamber at a uniform overpressure, where it is burned with a stationary flame. The overpressure must thereby be carefully adjusted as a function of the turbine load, the environmental conditions such as the pressure, quantity and temperature of the intake air, and the characteristics of the fuel (viscosity, ignition quality). The fuel pressure upstream of the fuel control unit must also be kept constant within strict limits.
For this purpose, feed pumps are primarily used, which feed pumps can be driven directly by the turbine. At these pumps, the injection pressure, and simultaneously the amount of fuel transported, must be adjusted by means of complex analog control mechanisms so that they correspond to the operating conditions indicated above. This system is excessively complex and expensive, in particular for small units, because the control valves used for the small amounts of fuel are expensive, and are very susceptible to fouling.
The same is true for feeding liquid fuels to other types of combustion chambers, e.g. for heating systems. In such a case, the feed for the fuel and the feed for the combustion air are generally driven by the same drive component, whereby the performance characteristics of the fan differ significantly from those of the fuel feed pump. Therefore, here again, a control system is required which includes sensitive and expensive valves which are susceptible to fouling.